| 1. |
- Grafström, Peter, et al.
(författare)
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Hyperfine structure and isotope shift of highly excited barium-I states
- 1982
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Ingår i: Zeitschrift für Physik A Hadrons and Nuclei. - 0939-7922. ; 306:4, s. 281-284
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution laser-spectroscopy measurements of hyperfine structure and isotope shifts were performed for the 6snd 1 D 2 sequence of Ba-I in the regionn=12–24. Stepwise laser excitations of a collimated atomic beam were used. A strong influence on the hyperfine structure is observed at the perturbation atn=14, caused by interaction with the 5d7d configuration. Whereas the isotope shift for the even isotopes stays essentially constant with increasingn, the odd isotopes exhibit a strong change, indicating hyperfine-induced shifts. Interesting discussions with Prof. E. Matthias in the final stage of this work are gratefully acknowledged. This work was supported by the Swedish Natural Science Research Council.
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| 2. |
- Jansson, Sune, 1962-
(författare)
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A Study on the Influence of Steel, Slag or Gas on Refractory Reactions
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the production of steel the oxide inclusion content partly depends on the reaction of the melt with the furnace lining, the ladle lining and the pouring system. The refractory material may be eroded by the molten steel and slag as well as corroded through chemical reactions with the slag and molten steel and the deoxidation products. In this report the effects of revolution speed, temperature and steel composition on the rate of dissolution of commercial MgO-C refractory samples into Al-deoxidised molten steel and CaOAl2O3- SiO2-MgO slag were examined by the rotating cylinder method. The study also includes tests with slag were doloma refractory samples are examined by the same method. Cylinders of MgO-C refractory material were immersed in to steel that was deoxidised by adding metallic aluminium. This was carried out in the temperature range of 1873 to 1973C° and at rotational speeds of 100 to 800 rpm for different holding times. The experimental results show that the rate of dissolution of MgO-C refractory materials increased with the temperature, rotational speed and immersion time. This supports the assumption that the diffusion of magnesium through the slag boundary layer formed around the refractory samples would be the rate-determining step. Mass transfer coefficients calculated on the basis of experimental results are in good agreement with earlier published results for pure ceramics. A formation of a thin oxide layer at the interface was found. It is due the reaction between magnesium vapour and the CO generated by the reaction MgO and C in the refractory walls. The oxide inclusions formed in the steel have been shown to mainly consist of MgO, Al2O3 and a mixture of them. The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing the molten slag similar to the MgO-C refractory/steel experiments. The corrosion rate was calculated from the change in diameter of the cylindrical specimens. The specimens were rotated for 15 to 120 minutes at speeds of 100 to 400 rpm in the molten slag. The rate of corrosion increased with temperature and with rotating speed of the rod and decreased when the slag was nearly saturated with MgO. The experimental results confirm the assumption that the diffusion of magnesium oxide through the slag phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of elements in the refractory materials into the slag, followed by penetration into the pores and grain boundaries. Finally, grains are loosened from the refractory into the slag. The investigation of doloma and doloma-carbon showed that the dissolution of magnesia into the slag was determining the corrosion rate. As for the other experiments, steel/MgO-C refractory and slag/MgO-C refractory, the corrosion rate was calculated from the change in diameter of the cylindrical specimens. The specimens were rotated for 15 to 120 minutes at speeds of 100 to 400 rpm in the molten slag. The results from the study showed that refractory materials that were impregnated with carbon had a much better slag resistance than the refractory that contained no carbon. This is due to the higher wetting angle between carbon and slag. Corrosion of MgO-C refractories in different gas atmospheres consisting of air, Ar, CO or Ar/CO was also studied. Experiments were carried out in the temperature range 1173 K to 1773 K and for holding times between 2 to 120 min. The reaction rate of the MgO-C material was determined from measurements of the weight loss of the samples. The results showed that the refractory weight loss increased with an increased temperature or an increased holding time. The thermodynamic conditions and the experimental results show that magnesium gas and carbon monoxide gas should form during ladle refining of steel when the refractory material consists of MgO-C.
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| 3. |
- Jansson, Sune, et al.
(författare)
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Corrosion mechanism and kinetic behaviour of MgO-C refractory material in contact with CaO-Al2O3-SiO2-MgO slag
- 2005
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 34:5, s. 283-292
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Tidskriftsartikel (refereegranskat)abstract
- The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical refractory specimens. The specimens were rotated for 15-120 min at a speed of 100-400 rpm in the molten slag. The rate of corrosion was found to increase with an increase in temperature and rod rotation speed, and to decrease when the slag was nearly saturated with MgO. The experimental results support the assumption that the diffusion of magnesium oxide through the slag-phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of refractory material into the slag followed by penetration of pores and grain boundaries and dispersion of the grains into the slag.
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| 4. |
- Jansson, Sune, et al.
(författare)
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Corrosion mechanism of commercial doloma refractories in contact with CaO-Al2O3-SiO2-MgO slag
- 2008
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 35:2, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution of three doloma based refractories in liquid CaO-Al2O3-SiO2-MgO slag was studied. Cylindrical refractory specimens of doloma, carbon bonded doloma, and magnesia doloma were rotated in a stationary crucible of molten slag under forced convection conditions. Slag composition, temperature, rod rotation speed and rod immersion time were varied. The refractory dissolution rate was determined from the change in diameter of the cylindrical specimens. The corrosion rate was found to increase with temperature and rod rotation speed and decrease when the slag was nearly saturated with MgO. The findings of the study substantiate the assumption that the diffusion of magnesium oxide through the slag boundary layer controls the corrosion process. The results indicated the overall corrosion process to be the dissolution of refractory material into the slag, followed by slag penetration of the pores and grain boundaries and finally, dispersion of the grains into the slag.
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| 5. |
- Jansson, Sune, et al.
(författare)
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Corrosion mechanism of commercial MgO-C refractories in contact with different gas atmospheres
- 2008
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:6, s. 760-767
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of MgO-C refractories in different gas atmospheres consisting of air, Ar, CO or Ar/CO was studied in laboratory experiments. In total, 103 experiments were carried out in the temperature range 1 173 to 1 773 K and for holding times between 2 to 120 min. The reaction rate of the MgO-C material was determined from measurements of the weight loss of the samples. The results showed that the refractory weight loss increased with an increased temperature or an increased holding time. The thermodynamic conditions and the experimental results showed that magnesium gas and carbon monoxide gas should form during ladle refining of steel when the refractory material consists of MgO-C. It was suggested that the reaction rate is directly dependent on the oxygen potential in the ambient atmosphere.
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| 6. |
- Jansson, Sune, et al.
(författare)
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Magnesia-carbon refractory dissolution in Al killed low carbon steel
- 2006
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 33:5, s. 389-397
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Tidskriftsartikel (refereegranskat)abstract
- The effects of rotation speed, steel temperature and steel composition on the rate of dissolution of MgO-C refractory into Al deoxidised molten steel were investigated using the rotating cylinder method. Cylinders or rods of MgO-C refractory material were immersed in an Al deoxidised molten steel. Experiments were performed for steel temperatures between 1873 and 1973 K and rotation speeds between 100 and 800 rev min(-1) as well as for different immersion times. For each case, the dissolution rate of MgO-C material was determined from measurement of the decrease in the rod radius. The experimental results showed that the dissolution rate of the MgO-C refractory material increased with an increase in steel temperature and rotation speed. The findings strongly suggest the diffusion of magnesium through the slag layer formed around the refractory rods to be a rate determining step. This thin oxide layer at the steel/refractory interface was found to be owing to reaction between magnesium vapour and CO generated by the reaction between MgO and C in the refractory. Oxide inclusions were also found in the steel melt and they were shown to mainly consist of MgO and Al2O3 or a mixture of the two.
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| 7. |
- Jiang, Z. K, et al.
(författare)
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Studies on radiative lifetimes in the 4d10ns2S and 4d10nd2D sequences of neutral silver
- 1990
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Ingår i: Zeitschrift für Physik D Atoms, Molecules and Clusters. - 0178-7683. ; 17:1, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- We have performed lifetime measurements in the sequences of2S1/2 and2D3/2 states for the alkali-like 4d10 ns,nd configurations of neutral silver. Selective stepwise excitations from the 4d10 5s2S1/2 ground state were performed using two pulsed dye lasers. Optical transients were recorded and evaluated with regard to the decay time. The lifetime results are compared with those of a theoretical study in which a model potential has been used to describe the polarisation of the 4d shell.
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| 8. |
- Jönsson, G., et al.
(författare)
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Natural radiative lifetimes in the 3 sns 1S0 and 3 snd 1D2 sequences of magnesium
- 1984
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Ingår i: Physical Review A. ; A30:5, s. 2429-2432
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Tidskriftsartikel (refereegranskat)abstract
- Natural radiative lifetimes have been determined in the determined in the 3 sns 1S0 (n=4-15) and the 3 snd 1D2 (n=3-15) sequences of Mg I employing a pulsed-laser system. The radiative lifetimes in the 1S0 sequence and of the higher members in the 1D2 sequence are unperturbed and scale as (n*)2.6 (where n* is the effective principal quantum number), while the lifetimes of the lower members in the 1D2 sequence are perturbed by the doubly excited 3p2 configuration. The measured lifetimes are compared with available theoretical calculations, and a very good agreement is obtained.
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| 9. |
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| 10. |
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